Rugby union, often referred to simply as rugby, is a full contact team sport which originated in England in the early 19th century.[2] One of the two codes of rugby football, it is based on running with the ball in hand. In its most common form a game is between two teams of 15 players using an oval-shaped ball on a field with H-shaped goalposts on each goal line. William Webb Ellis is often credited with the invention of running with the ball in hand in 1823 at Rugby School when he allegedly caught the ball while playing football and ran towards the opposition goal. However, the evidence for the story is doubtful. In 1845, the first football laws were written by Rugby School pupils; other significant events in the early development of rugby include the Blackheath Club's decision to leave the Football Association in 1863 and the split between rugby union and rugby league in 1895. Historically an amateur sport, in 1995 the International Rugby Board (IRB) removed restrictions on payments to players, making the game openly professional at the highest level for the first time. The IRB has been the governing body for rugby union since its formation in 1886. Rugby union spread from the Home Nations of Great Britain and Ireland, and was absorbed by many of the countries associated with the British Empire. Early exponents of the sport included Australia, New Zealand and South Africa. Countries that have adopted rugby union as theirde facto national sport include Fiji, Georgia, New Zealand, Samoa, Tonga and Wales. Rugby union is played in over 100 countries across six continents and as of 27 November 2012, the IRB has 100 full members and 18 associate members. The Rugby World Cup, first held in 1987, takes place every four years with the winner of the tournament receiving the Webb Ellis Cup. The Six Nations Championship in Europe and The Rugby Championship in the Southern Hemisphere (the latter replacing the Tri Nations) are major international competitions held annually. Major domestic competitions include the English Premiership in England, Top 14 in France, the Currie Cup in South Africa, and the ITM Cup in New Zealand. Other transnational competitions include the Pro 12, involving Irish, Italian, Scottish and Welsh teams; the Heineken Cup, involving the top European teams from their respective domestic competitions; and Super Rugby, involving Australian, New Zealand and South African teams.